Integrated amplifier arrangement

ABSTRACT

A millimetric-wave amplifier arrangement comprises a first amplifier whose output is connected to one input of the second amplifier via an adjustable attenuator. Both amplifiers are integrated on a single substrate.

The present invention concerns an integrated amplifier arrangement forhigh frequency signals in the millimeter wave range.

Monolithically integrated millimeter wave amplifiers are known in aone-stage and two-stage form, i.e., in the form of two one-stageamplifiers connected in series on a common substrate. Two-stageamplifiers are used when amplification that cannot be easily achievedwith one stage amplifiers is necessary. However, relative to one-stageamplifiers they have the drawback that the signal level range in whichamplification is possible with sufficient linearity is smaller than in aone-stage amplifier, since a signal that is amplified with good qualityby one-stage amplifier or the first stage of a two-stage amplifier caneasily reach a level that leads to saturation of the second amplifierstage. For applications in which this hazard exists, hybrid circuits aretherefore ordinarily used, which are constructed from a first and secondamplifier, each integrated on its own substrate, and a controllableattenuator inserted in between, which serves to throttle the level ofthe output signal of the first amplifier stage, if necessary, far enoughso that sufficiently linear amplification is again possible in thesecond amplifier stage.

Such hybrid circuits require considerable circuit board space because ofthe large number of discrete components. In addition, their manufactureis demanding and costly, since placement and bonding of these discretecomponents must occur with high precision in order to achieve thedesired properties of the finished amplifier.

The task of the present invention is to devise an integrated millimeterwave amplifier arrangement that permits amplification of input signalswith good linearity over a large level range and is simply, costeffective, and space-saving in application.

The task is solved according to the invention in that in a millimeterwave amplifier arrangement with two amplifiers integrated on a commonsubstrate, one output of the first amplifier is connected to an outputof the second amplifier via a controllable attenuator.

If this controllable attenuator is integrated together with theamplifiers on the same substrate, any problems of placement of theamplifiers and attenuator relative to each other are eliminated, sincetheir position relative to each other is reproducibly stipulated by amask used for production. If the controllable attenuator is formed on adifferent substrate than the amplifier, the problems during placementare also reduced, since only two substrates still need be positionedrelative to each other and not free in the usual manner.

The controllable attenuator preferably includes a four-port interdigitalcoupler, generally also referred to as a Lange coupler, which isintegrated with the amplifiers on the same substrate and has a firstport connected to the output of the first amplifier and a second portconnected to the input of the second amplifier.

The controllable attenuator also preferably includes controllableresistors connected to a third and fourth port of Lange coupler. Thesecontrollable resistors can be integrated on the same substrate as theamplifiers; however, they can also be situated on a different substrateso that different production techniques can be used for the amplifiersand for the controllable resistors.

In the latter case controllable resistors are preferably connected tothe third and fourth ports of the Lange coupler via conducting airbridges.

PIN diodes or FETs are considered in particular as controllableresistors.

The resistance value of these controllable resistors is controlled bymeans of a control voltage, a dc voltage in the forward direction in PINdiodes and a gate-source voltage in FETs. At least one dc source tosupply this control voltage is preferably integrated with the amplifieron the substrate. This dc source can be a control circuit that receivesthe output signal of the first amplifier or the input signal of thesecond amplifier and fixes the dc voltage level with reference to thesignal level of this received signal.

A Lange coupler which is transmitting for a dc voltage between all ofits four ports is preferably used in the amplifier arrangement accordingto the invention. In this case a single dc voltage source is sufficientto supply both controllable resistors with the control voltage.

In order to decouple the first and/or second amplifier from the controlvoltage of the dc voltage source, a capacitor is preferably arrangedbetween the output of the first amplifier and/or the input of the secondamplifier and the corresponding port of the Lange coupler.

Additional features and advantages of the invention are apparent fromthe following description of the practical examples with reference tothe accompanying figures. In the figures:

FIG. 1 schematically depicts a chip layout according to the firstpractical example of the invention;

FIG. 2 shows an example for a chip layout according to the secondembodiment of the invention; and

FIG. 3 shows an example for a chip layout according to the thirdembodiment of the invention.

The following are patterned on a semiconductor substrate 1 depicted as acutout in FIG. 1: first amplifier 2, second amplifier 3, a Lange coupler4, two controllable resistors 5, 6 and two control circuits 7, 8.

One input of the first amplifier 2 is connected to a source (not shown)for a millimeter wave signal being amplified, which can lie outside ofthe semiconductor substrate 1. The output of amplifier 2 is connectedvia a capacitor 9 to a first port 11 ₁ of the Lange coupler. The Langecoupler includes five parallel printed conductors 12 ₁, 12 ₂, . . . , 12₅. The middle printed conductor 12 ₃ represents a galvanic connectionbetween port 11 ₁ and a diagonally opposite port 11 ₃. It is connectedin the center via air bridges 13 to the next adjacent printed conductors12 ₁, 12 ₅ emerging from ports 11 ₁ and 11 ₃. Printed conductors 12 ₂,12 ₄ extending on both sides of printed conductor 12 ₃ each emerge fromports 11 ₂ and 11 ₄ and are also connected on their ends by air bridges13.

The input of the second amplifier 3 is connected to the second port 11 ₂via a capacitor 10. A controllable resistor 5 and 6 and a controlcircuit 7 and 8 connected to it are connected to ports 11 ₃, 11 ₄. Thecontrol circuits 7, 8 are constructed identically and connected to thesame input signal. This input signal, as shown by the dashed connection14, can be derived from the output of the first amplifier 2 so that thecontrol circuits 7, 8 produce an attenuation current I_(ATT) to thecontrollable resistors 5, 6, which is stipulated as a function of theoutput level of the first amplifier 2 so that the input signal of thesecond amplifier 3 always lies reliably in this linear range.

The controllable resistances 5, 6 are implemented as PIN diodes here,each of which has an electrode connected to ground and which aretraversed in the forward direction by the attenuation current I_(ATT).As an alternative, an implementation in the form of field effecttransistors would also be possible, with current running through drainand source current between the connected port 11 ₃ or 11 ₄ of the Langecoupler and ground, and with a resistor controlled by a voltage appliedto the gate of the FET by the control circuit 7 or 8.

FIG. 2 shows a further developed embodiment of the amplifier arrangementaccording to the invention. Elements of this arrangement that correspondto elements already described with reference to FIG. 1 have the samereference numbers and are not described again.

The difference between this embodiment and that of FIG. 1 is anadditional line 12 ₀ of the Lange coupler 4. The printed conductor 12 ₀emerging from port 11 ₁ is twice as long as the printed conductor 12 ₁adjacent to it, but is folded back on half its length so that the tip ofprinted conductor 12 ₀ lies in the immediate vicinity of port 11 ₁. Thistip is connected via an additional air bridge 13 to the tip of theprinted conductor 12 ₂ emerging from port 11 ₂. This additional airbridge 13 guarantees a galvanic connection between all four ports of theLange coupler 4. A single control circuit 7 is therefore sufficient toproduce an attenuation current I_(ATT) with which both controllableresistors 5, 6 are supplied. The control circuit 7 is connected here toport 11 ₂ so that the control current to both controllable resistors 5,6 must flow through at least one of the printed conductors of the Langecoupler. The printed conductors of the Lange coupler 4 therefore form aseries resistance for the attenuation current I_(ATT) in series with thecontrollable resistance 5, 6, but which leads to no asymmetry in thebehavior of the controllable resistors since it is essentially the samefor both controllable resistors 5, 6. Such asymmetry can occur if thecontrol circuit 7 were to be directly connected to one of the ports 11₃, 11 ₄.

The practical example of FIG. 3 differs from that of FIG. 2 in that thecontrollable resistors 6, 7 here are implemented outside of thesemiconductor substrate 1 as separate components, and are connected tothe corresponding ports 11 ₃, 11 ₄ of the Lange coupler 4 via airbridges 15. This embodiment permits different production technologies tobe used to produce the controllable resistors than for amplifiers 2, 3and Lange coupler 4. Since the Lange coupler 4 is integrated togetherwith the amplifiers 2, 3 on the same substrate 1, phase shifts of thesignal being amplified can be controlled precisely between the twoamplifiers 2, 3 and are uniform for all amplifiers of a series, sincethey are stipulated by the structure of the employed mask.

1-8. (canceled)
 9. A millimeter wave amplifier arrangement, comprising:first and second amplifiers integrated on a common substrate, the firstamplifier having an output connected to an input of the second amplifiervia a controllable attenuator.
 10. The millimeter wave amplifierarrangement according to claim 9, in that the controllable attenuatorincludes a Lange coupler having one port connected to the output of thefirst amplifier, and an additional port connected to the input of thesecond amplifier, and in that the Lange coupler is integrated with theamplifiers on the common substrate.
 11. The millimeter wave amplifierarrangement according to claim 10, in that the controllable attenuatoralso includes controllable resistors connected to a third and a fourthport of the Lange coupler, and in that the resistors are integrated onthe common substrate.
 12. The millimeter wave amplifier arrangementaccording to claim 10, in that the controllable attenuator also includescontrollable resistors arranged outside of the common substrate andconnected to a third and a fourth port of the Lange coupler viaconducting air bridges.
 13. The millimeter wave amplifier arrangementaccording to claim 11, in that the controllable resistors are formed byPIN diodes or field effect transistors.
 14. The millimeter waveamplifier arrangement according to claim 12, in that the controllableresistors are formed by PIN diodes or field effect transistors.
 15. Themillimeter wave amplifier arrangement according to claim 11, in that atleast one voltage source is integrated on the common substrate todeliver a control voltage for the controllable resistors.
 16. Themillimeter wave amplifier arrangement according to claim 12, in that atleast one voltage source is integrated on the common substrate todeliver a control voltage for the controllable resistors.
 17. Themillimeter wave amplifier arrangement according to claim 15, in that theLange coupler conducts the control voltage between all ports of theLange coupler, and in that the at least one voltage source supplies thecontrol voltage to both controllable resistors.
 18. The millimeter waveamplifier arrangement according to claim 17, in that at least one of theoutput of the first amplifier and the input of the second amplifier isconnected to a corresponding port of the Lange coupler via a capacitor.